The present invention relates to an improved edge dam for use with applicators of the trailing blade type for applying a coating liquid to a web of moving paper.
Conventional applicators of the trailing blade type include means for applying coating material to a paper web that is usually supported and carried by a resilient backing roll. Such applicators may include a chamber having an opening extending across and parallel to the web, together with a doctor blade located on a trailing side of the opening, which serves to level the coating, and a front wall extending from a leading side of the opening toward the web. Means are provided for supplying a coating liquid to the chamber, and thence through the chamber opening and between the front wall and doctor blade to the web. To seal the end spaces between the front wall and doctor blade to prevent escape of coating material laterally of the web, edge dam means are provided thereat.
For applicators of the foregoing types, the edge dam means may comprise a flexible element at each end space for sealing with the front wall, doctor blade and paper web. Ideally, the edge dam absolutely prevents passage of any coating liquid to exterior of the chamber. However, in practice coating liquid often leaks past the edge dam, with the result that the backing roll or web edges become contaminated, for example by stickers on the roll of coated paper.